/*
   * Copyright (C) Sistina Software, Inc.  1997-2003 All rights reserved.

   * Copyright (C) 2004-2006 Red Hat, Inc.  All rights reserved.

   *
   * This copyrighted material is made available to anyone wishing to use,
   * modify, copy, or redistribute it subject to the terms and conditions

   * of the GNU General Public License version 2.

   */

  #include <linux/spinlock.h>
  #include <linux/completion.h>
  #include <linux/buffer_head.h>

  #include <linux/blkdev.h>

  #include <linux/gfs2_ondisk.h>

  #include <linux/crc32.h>

  
  #include "gfs2.h"

  #include "incore.h"

  #include "bmap.h"
  #include "glock.h"
  #include "inode.h"

  #include "meta_io.h"

  #include "quota.h"
  #include "rgrp.h"

  #include "super.h"

  #include "trans.h"

  #include "dir.h"

  #include "util.h"

  #include "trace_gfs2.h"

  
  /* This doesn't need to be that large as max 64 bit pointers in a 4k
   * block is 512, so __u16 is fine for that. It saves stack space to
   * keep it small.
   */
  struct metapath {

  	struct buffer_head *mp_bh[GFS2_MAX_META_HEIGHT];

  	__u16 mp_list[GFS2_MAX_META_HEIGHT];
  };

  struct strip_mine {
  	int sm_first;
  	unsigned int sm_height;
  };
  
  /**

   * gfs2_unstuffer_page - unstuff a stuffed inode into a block cached by a page
   * @ip: the inode
   * @dibh: the dinode buffer
   * @block: the block number that was allocated

   * @page: The (optional) page. This is looked up if @page is NULL

   *
   * Returns: errno
   */
  
  static int gfs2_unstuffer_page(struct gfs2_inode *ip, struct buffer_head *dibh,

  			       u64 block, struct page *page)

  {

  	struct inode *inode = &ip->i_inode;
  	struct buffer_head *bh;
  	int release = 0;
  
  	if (!page || page->index) {
  		page = grab_cache_page(inode->i_mapping, 0);
  		if (!page)
  			return -ENOMEM;
  		release = 1;
  	}
  
  	if (!PageUptodate(page)) {
  		void *kaddr = kmap(page);

  		u64 dsize = i_size_read(inode);
   
  		if (dsize > (dibh->b_size - sizeof(struct gfs2_dinode)))
  			dsize = dibh->b_size - sizeof(struct gfs2_dinode);

  		memcpy(kaddr, dibh->b_data + sizeof(struct gfs2_dinode), dsize);
  		memset(kaddr + dsize, 0, PAGE_CACHE_SIZE - dsize);

  		kunmap(page);
  
  		SetPageUptodate(page);
  	}
  
  	if (!page_has_buffers(page))
  		create_empty_buffers(page, 1 << inode->i_blkbits,
  				     (1 << BH_Uptodate));
  
  	bh = page_buffers(page);
  
  	if (!buffer_mapped(bh))
  		map_bh(bh, inode->i_sb, block);
  
  	set_buffer_uptodate(bh);

  	if (!gfs2_is_jdata(ip))
  		mark_buffer_dirty(bh);

  	if (!gfs2_is_writeback(ip))

  		gfs2_trans_add_bh(ip->i_gl, bh, 0);

  
  	if (release) {
  		unlock_page(page);
  		page_cache_release(page);
  	}
  
  	return 0;
  }
  
  /**

   * gfs2_unstuff_dinode - Unstuff a dinode when the data has grown too big
   * @ip: The GFS2 inode to unstuff

   * @page: The (optional) page. This is looked up if the @page is NULL

   *
   * This routine unstuffs a dinode and returns it to a "normal" state such
   * that the height can be grown in the traditional way.
   *
   * Returns: errno
   */

  int gfs2_unstuff_dinode(struct gfs2_inode *ip, struct page *page)

  {
  	struct buffer_head *bh, *dibh;

  	struct gfs2_dinode *di;

  	u64 block = 0;

  	int isdir = gfs2_is_dir(ip);

  	int error;
  
  	down_write(&ip->i_rw_mutex);
  
  	error = gfs2_meta_inode_buffer(ip, &dibh);
  	if (error)
  		goto out;

  	if (i_size_read(&ip->i_inode)) {

  		/* Get a free block, fill it with the stuffed data,
  		   and write it out to disk */

  		unsigned int n = 1;

  		error = gfs2_alloc_blocks(ip, &block, &n, 0, NULL);

  		if (error)
  			goto out_brelse;

  		if (isdir) {

  			gfs2_trans_add_unrevoke(GFS2_SB(&ip->i_inode), block, 1);

  			error = gfs2_dir_get_new_buffer(ip, block, &bh);

  			if (error)
  				goto out_brelse;

  			gfs2_buffer_copy_tail(bh, sizeof(struct gfs2_meta_header),

  					      dibh, sizeof(struct gfs2_dinode));
  			brelse(bh);
  		} else {

  			error = gfs2_unstuffer_page(ip, dibh, block, page);

  			if (error)
  				goto out_brelse;
  		}
  	}
  
  	/*  Set up the pointer to the new block  */

  	gfs2_trans_add_bh(ip->i_gl, dibh, 1);

  	di = (struct gfs2_dinode *)dibh->b_data;

  	gfs2_buffer_clear_tail(dibh, sizeof(struct gfs2_dinode));

  	if (i_size_read(&ip->i_inode)) {

  		*(__be64 *)(di + 1) = cpu_to_be64(block);

  		gfs2_add_inode_blocks(&ip->i_inode, 1);
  		di->di_blocks = cpu_to_be64(gfs2_get_inode_blocks(&ip->i_inode));

  	}

  	ip->i_height = 1;

  	di->di_height = cpu_to_be16(1);

  out_brelse:

  	brelse(dibh);

  out:

  	up_write(&ip->i_rw_mutex);

  	return error;
  }

  
  /**
   * find_metapath - Find path through the metadata tree

   * @sdp: The superblock

   * @mp: The metapath to return the result in
   * @block: The disk block to look up

   * @height: The pre-calculated height of the metadata tree

   *
   *   This routine returns a struct metapath structure that defines a path
   *   through the metadata of inode "ip" to get to block "block".
   *
   *   Example:
   *   Given:  "ip" is a height 3 file, "offset" is 101342453, and this is a
   *   filesystem with a blocksize of 4096.
   *
   *   find_metapath() would return a struct metapath structure set to:
   *   mp_offset = 101342453, mp_height = 3, mp_list[0] = 0, mp_list[1] = 48,
   *   and mp_list[2] = 165.
   *
   *   That means that in order to get to the block containing the byte at
   *   offset 101342453, we would load the indirect block pointed to by pointer
   *   0 in the dinode.  We would then load the indirect block pointed to by
   *   pointer 48 in that indirect block.  We would then load the data block
   *   pointed to by pointer 165 in that indirect block.
   *
   *             ----------------------------------------
   *             | Dinode |                             |
   *             |        |                            4|
   *             |        |0 1 2 3 4 5                 9|
   *             |        |                            6|
   *             ----------------------------------------
   *                       |
   *                       |
   *                       V
   *             ----------------------------------------
   *             | Indirect Block                       |
   *             |                                     5|
   *             |            4 4 4 4 4 5 5            1|
   *             |0           5 6 7 8 9 0 1            2|
   *             ----------------------------------------
   *                                |
   *                                |
   *                                V
   *             ----------------------------------------
   *             | Indirect Block                       |
   *             |                         1 1 1 1 1   5|
   *             |                         6 6 6 6 6   1|
   *             |0                        3 4 5 6 7   2|
   *             ----------------------------------------
   *                                           |
   *                                           |
   *                                           V
   *             ----------------------------------------
   *             | Data block containing offset         |
   *             |            101342453                 |
   *             |                                      |
   *             |                                      |
   *             ----------------------------------------
   *
   */

  static void find_metapath(const struct gfs2_sbd *sdp, u64 block,
  			  struct metapath *mp, unsigned int height)

  {

  	unsigned int i;

  	for (i = height; i--;)

  		mp->mp_list[i] = do_div(block, sdp->sd_inptrs);

  
  }

  static inline unsigned int metapath_branch_start(const struct metapath *mp)

  {

  	if (mp->mp_list[0] == 0)
  		return 2;
  	return 1;

  }

  /**
   * metapointer - Return pointer to start of metadata in a buffer

   * @height: The metadata height (0 = dinode)
   * @mp: The metapath
   *
   * Return a pointer to the block number of the next height of the metadata
   * tree given a buffer containing the pointer to the current height of the
   * metadata tree.
   */

  static inline __be64 *metapointer(unsigned int height, const struct metapath *mp)

  {

  	struct buffer_head *bh = mp->mp_bh[height];

  	unsigned int head_size = (height > 0) ?
  		sizeof(struct gfs2_meta_header) : sizeof(struct gfs2_dinode);

  	return ((__be64 *)(bh->b_data + head_size)) + mp->mp_list[height];

  }

  static void gfs2_metapath_ra(struct gfs2_glock *gl,
  			     const struct buffer_head *bh, const __be64 *pos)
  {
  	struct buffer_head *rabh;
  	const __be64 *endp = (const __be64 *)(bh->b_data + bh->b_size);
  	const __be64 *t;
  
  	for (t = pos; t < endp; t++) {
  		if (!*t)
  			continue;
  
  		rabh = gfs2_getbuf(gl, be64_to_cpu(*t), CREATE);
  		if (trylock_buffer(rabh)) {
  			if (!buffer_uptodate(rabh)) {
  				rabh->b_end_io = end_buffer_read_sync;
  				submit_bh(READA | REQ_META, rabh);
  				continue;
  			}
  			unlock_buffer(rabh);
  		}
  		brelse(rabh);
  	}
  }

  /**

   * lookup_metapath - Walk the metadata tree to a specific point
   * @ip: The inode

   * @mp: The metapath

   *

   * Assumes that the inode's buffer has already been looked up and
   * hooked onto mp->mp_bh[0] and that the metapath has been initialised
   * by find_metapath().
   *
   * If this function encounters part of the tree which has not been
   * allocated, it returns the current height of the tree at the point
   * at which it found the unallocated block. Blocks which are found are
   * added to the mp->mp_bh[] list.

   *

   * Returns: error or height of metadata tree

   */

  static int lookup_metapath(struct gfs2_inode *ip, struct metapath *mp)

  {

  	unsigned int end_of_metadata = ip->i_height - 1;
  	unsigned int x;

  	__be64 *ptr;
  	u64 dblock;

  	int ret;

  
  	for (x = 0; x < end_of_metadata; x++) {

  		ptr = metapointer(x, mp);
  		dblock = be64_to_cpu(*ptr);
  		if (!dblock)
  			return x + 1;

  		ret = gfs2_meta_indirect_buffer(ip, x+1, dblock, 0, &mp->mp_bh[x+1]);

  		if (ret)
  			return ret;
  	}

  	return ip->i_height;

  }

  static inline void release_metapath(struct metapath *mp)

  {
  	int i;

  	for (i = 0; i < GFS2_MAX_META_HEIGHT; i++) {
  		if (mp->mp_bh[i] == NULL)
  			break;
  		brelse(mp->mp_bh[i]);
  	}

  }

  /**
   * gfs2_extent_length - Returns length of an extent of blocks
   * @start: Start of the buffer
   * @len: Length of the buffer in bytes
   * @ptr: Current position in the buffer
   * @limit: Max extent length to return (0 = unlimited)
   * @eob: Set to 1 if we hit "end of block"
   *
   * If the first block is zero (unallocated) it will return the number of
   * unallocated blocks in the extent, otherwise it will return the number
   * of contiguous blocks in the extent.
   *
   * Returns: The length of the extent (minimum of one block)
   */
  
  static inline unsigned int gfs2_extent_length(void *start, unsigned int len, __be64 *ptr, unsigned limit, int *eob)
  {
  	const __be64 *end = (start + len);
  	const __be64 *first = ptr;
  	u64 d = be64_to_cpu(*ptr);
  
  	*eob = 0;
  	do {
  		ptr++;
  		if (ptr >= end)
  			break;
  		if (limit && --limit == 0)
  			break;
  		if (d)
  			d++;
  	} while(be64_to_cpu(*ptr) == d);
  	if (ptr >= end)
  		*eob = 1;
  	return (ptr - first);
  }

  static inline void bmap_lock(struct gfs2_inode *ip, int create)

  {

  	if (create)
  		down_write(&ip->i_rw_mutex);
  	else
  		down_read(&ip->i_rw_mutex);
  }

  static inline void bmap_unlock(struct gfs2_inode *ip, int create)

  {

  	if (create)
  		up_write(&ip->i_rw_mutex);
  	else
  		up_read(&ip->i_rw_mutex);
  }

  static inline __be64 *gfs2_indirect_init(struct metapath *mp,
  					 struct gfs2_glock *gl, unsigned int i,
  					 unsigned offset, u64 bn)
  {
  	__be64 *ptr = (__be64 *)(mp->mp_bh[i - 1]->b_data +
  		       ((i > 1) ? sizeof(struct gfs2_meta_header) :
  				 sizeof(struct gfs2_dinode)));
  	BUG_ON(i < 1);
  	BUG_ON(mp->mp_bh[i] != NULL);
  	mp->mp_bh[i] = gfs2_meta_new(gl, bn);
  	gfs2_trans_add_bh(gl, mp->mp_bh[i], 1);
  	gfs2_metatype_set(mp->mp_bh[i], GFS2_METATYPE_IN, GFS2_FORMAT_IN);
  	gfs2_buffer_clear_tail(mp->mp_bh[i], sizeof(struct gfs2_meta_header));
  	ptr += offset;
  	*ptr = cpu_to_be64(bn);
  	return ptr;
  }
  
  enum alloc_state {
  	ALLOC_DATA = 0,
  	ALLOC_GROW_DEPTH = 1,
  	ALLOC_GROW_HEIGHT = 2,
  	/* ALLOC_UNSTUFF = 3,   TBD and rather complicated */
  };
  
  /**
   * gfs2_bmap_alloc - Build a metadata tree of the requested height
   * @inode: The GFS2 inode
   * @lblock: The logical starting block of the extent
   * @bh_map: This is used to return the mapping details
   * @mp: The metapath
   * @sheight: The starting height (i.e. whats already mapped)
   * @height: The height to build to
   * @maxlen: The max number of data blocks to alloc
   *
   * In this routine we may have to alloc:
   *   i) Indirect blocks to grow the metadata tree height
   *  ii) Indirect blocks to fill in lower part of the metadata tree
   * iii) Data blocks
   *
   * The function is in two parts. The first part works out the total
   * number of blocks which we need. The second part does the actual
   * allocation asking for an extent at a time (if enough contiguous free
   * blocks are available, there will only be one request per bmap call)
   * and uses the state machine to initialise the blocks in order.
   *
   * Returns: errno on error
   */
  
  static int gfs2_bmap_alloc(struct inode *inode, const sector_t lblock,
  			   struct buffer_head *bh_map, struct metapath *mp,
  			   const unsigned int sheight,
  			   const unsigned int height,
  			   const unsigned int maxlen)
  {
  	struct gfs2_inode *ip = GFS2_I(inode);
  	struct gfs2_sbd *sdp = GFS2_SB(inode);

  	struct super_block *sb = sdp->sd_vfs;

  	struct buffer_head *dibh = mp->mp_bh[0];
  	u64 bn, dblock = 0;

  	unsigned n, i, blks, alloced = 0, iblks = 0, branch_start = 0;

  	unsigned dblks = 0;
  	unsigned ptrs_per_blk;
  	const unsigned end_of_metadata = height - 1;

  	int ret;

  	int eob = 0;
  	enum alloc_state state;
  	__be64 *ptr;
  	__be64 zero_bn = 0;
  
  	BUG_ON(sheight < 1);
  	BUG_ON(dibh == NULL);
  
  	gfs2_trans_add_bh(ip->i_gl, dibh, 1);
  
  	if (height == sheight) {
  		struct buffer_head *bh;
  		/* Bottom indirect block exists, find unalloced extent size */
  		ptr = metapointer(end_of_metadata, mp);
  		bh = mp->mp_bh[end_of_metadata];
  		dblks = gfs2_extent_length(bh->b_data, bh->b_size, ptr, maxlen,
  					   &eob);
  		BUG_ON(dblks < 1);
  		state = ALLOC_DATA;
  	} else {
  		/* Need to allocate indirect blocks */
  		ptrs_per_blk = height > 1 ? sdp->sd_inptrs : sdp->sd_diptrs;
  		dblks = min(maxlen, ptrs_per_blk - mp->mp_list[end_of_metadata]);
  		if (height == ip->i_height) {
  			/* Writing into existing tree, extend tree down */
  			iblks = height - sheight;
  			state = ALLOC_GROW_DEPTH;
  		} else {
  			/* Building up tree height */
  			state = ALLOC_GROW_HEIGHT;
  			iblks = height - ip->i_height;

  			branch_start = metapath_branch_start(mp);
  			iblks += (height - branch_start);

  		}
  	}
  
  	/* start of the second part of the function (state machine) */
  
  	blks = dblks + iblks;
  	i = sheight;
  	do {

  		int error;

  		n = blks - alloced;

  		error = gfs2_alloc_blocks(ip, &bn, &n, 0, NULL);

  		if (error)
  			return error;

  		alloced += n;
  		if (state != ALLOC_DATA || gfs2_is_jdata(ip))
  			gfs2_trans_add_unrevoke(sdp, bn, n);
  		switch (state) {
  		/* Growing height of tree */
  		case ALLOC_GROW_HEIGHT:
  			if (i == 1) {
  				ptr = (__be64 *)(dibh->b_data +
  						 sizeof(struct gfs2_dinode));
  				zero_bn = *ptr;
  			}
  			for (; i - 1 < height - ip->i_height && n > 0; i++, n--)
  				gfs2_indirect_init(mp, ip->i_gl, i, 0, bn++);
  			if (i - 1 == height - ip->i_height) {
  				i--;
  				gfs2_buffer_copy_tail(mp->mp_bh[i],
  						sizeof(struct gfs2_meta_header),
  						dibh, sizeof(struct gfs2_dinode));
  				gfs2_buffer_clear_tail(dibh,
  						sizeof(struct gfs2_dinode) +
  						sizeof(__be64));
  				ptr = (__be64 *)(mp->mp_bh[i]->b_data +
  					sizeof(struct gfs2_meta_header));
  				*ptr = zero_bn;
  				state = ALLOC_GROW_DEPTH;

  				for(i = branch_start; i < height; i++) {

  					if (mp->mp_bh[i] == NULL)
  						break;
  					brelse(mp->mp_bh[i]);
  					mp->mp_bh[i] = NULL;
  				}

  				i = branch_start;

  			}
  			if (n == 0)
  				break;
  		/* Branching from existing tree */
  		case ALLOC_GROW_DEPTH:
  			if (i > 1 && i < height)
  				gfs2_trans_add_bh(ip->i_gl, mp->mp_bh[i-1], 1);
  			for (; i < height && n > 0; i++, n--)
  				gfs2_indirect_init(mp, ip->i_gl, i,
  						   mp->mp_list[i-1], bn++);
  			if (i == height)
  				state = ALLOC_DATA;
  			if (n == 0)
  				break;
  		/* Tree complete, adding data blocks */
  		case ALLOC_DATA:
  			BUG_ON(n > dblks);
  			BUG_ON(mp->mp_bh[end_of_metadata] == NULL);
  			gfs2_trans_add_bh(ip->i_gl, mp->mp_bh[end_of_metadata], 1);
  			dblks = n;
  			ptr = metapointer(end_of_metadata, mp);
  			dblock = bn;
  			while (n-- > 0)
  				*ptr++ = cpu_to_be64(bn++);

  			if (buffer_zeronew(bh_map)) {
  				ret = sb_issue_zeroout(sb, dblock, dblks,
  						       GFP_NOFS);
  				if (ret) {
  					fs_err(sdp,
  					       "Failed to zero data buffers
  ");
  					clear_buffer_zeronew(bh_map);
  				}
  			}

  			break;
  		}

  	} while ((state != ALLOC_DATA) || !dblock);

  
  	ip->i_height = height;
  	gfs2_add_inode_blocks(&ip->i_inode, alloced);
  	gfs2_dinode_out(ip, mp->mp_bh[0]->b_data);
  	map_bh(bh_map, inode->i_sb, dblock);
  	bh_map->b_size = dblks << inode->i_blkbits;
  	set_buffer_new(bh_map);
  	return 0;
  }

  /**

   * gfs2_block_map - Map a block from an inode to a disk block

   * @inode: The inode

   * @lblock: The logical block number

   * @bh_map: The bh to be mapped

   * @create: True if its ok to alloc blocks to satify the request

   *

   * Sets buffer_mapped() if successful, sets buffer_boundary() if a
   * read of metadata will be required before the next block can be
   * mapped. Sets buffer_new() if new blocks were allocated.

   *
   * Returns: errno
   */

  int gfs2_block_map(struct inode *inode, sector_t lblock,
  		   struct buffer_head *bh_map, int create)

  {

  	struct gfs2_inode *ip = GFS2_I(inode);
  	struct gfs2_sbd *sdp = GFS2_SB(inode);

  	unsigned int bsize = sdp->sd_sb.sb_bsize;

  	const unsigned int maxlen = bh_map->b_size >> inode->i_blkbits;

  	const u64 *arr = sdp->sd_heightsize;

  	__be64 *ptr;
  	u64 size;
  	struct metapath mp;
  	int ret;
  	int eob;
  	unsigned int len;
  	struct buffer_head *bh;
  	u8 height;

  	BUG_ON(maxlen == 0);

  	memset(mp.mp_bh, 0, sizeof(mp.mp_bh));

  	bmap_lock(ip, create);

  	clear_buffer_mapped(bh_map);
  	clear_buffer_new(bh_map);
  	clear_buffer_boundary(bh_map);

  	trace_gfs2_bmap(ip, bh_map, lblock, create, 1);

  	if (gfs2_is_dir(ip)) {
  		bsize = sdp->sd_jbsize;
  		arr = sdp->sd_jheightsize;
  	}

  	ret = gfs2_meta_inode_buffer(ip, &mp.mp_bh[0]);
  	if (ret)
  		goto out;

  	height = ip->i_height;
  	size = (lblock + 1) * bsize;
  	while (size > arr[height])
  		height++;
  	find_metapath(sdp, lblock, &mp, height);
  	ret = 1;
  	if (height > ip->i_height || gfs2_is_stuffed(ip))
  		goto do_alloc;
  	ret = lookup_metapath(ip, &mp);
  	if (ret < 0)
  		goto out;
  	if (ret != ip->i_height)
  		goto do_alloc;
  	ptr = metapointer(ip->i_height - 1, &mp);
  	if (*ptr == 0)
  		goto do_alloc;
  	map_bh(bh_map, inode->i_sb, be64_to_cpu(*ptr));
  	bh = mp.mp_bh[ip->i_height - 1];
  	len = gfs2_extent_length(bh->b_data, bh->b_size, ptr, maxlen, &eob);
  	bh_map->b_size = (len << inode->i_blkbits);
  	if (eob)
  		set_buffer_boundary(bh_map);
  	ret = 0;
  out:
  	release_metapath(&mp);

  	trace_gfs2_bmap(ip, bh_map, lblock, create, ret);

  	bmap_unlock(ip, create);
  	return ret;

  do_alloc:
  	/* All allocations are done here, firstly check create flag */
  	if (!create) {
  		BUG_ON(gfs2_is_stuffed(ip));
  		ret = 0;
  		goto out;

  	}

  
  	/* At this point ret is the tree depth of already allocated blocks */
  	ret = gfs2_bmap_alloc(inode, lblock, bh_map, &mp, ret, height, maxlen);
  	goto out;

  }

  /*
   * Deprecated: do not use in new code
   */

  int gfs2_extent_map(struct inode *inode, u64 lblock, int *new, u64 *dblock, unsigned *extlen)
  {

  	struct buffer_head bh = { .b_state = 0, .b_blocknr = 0 };

  	int ret;

  	int create = *new;
  
  	BUG_ON(!extlen);
  	BUG_ON(!dblock);
  	BUG_ON(!new);

  	bh.b_size = 1 << (inode->i_blkbits + (create ? 0 : 5));

  	ret = gfs2_block_map(inode, lblock, &bh, create);

  	*extlen = bh.b_size >> inode->i_blkbits;
  	*dblock = bh.b_blocknr;
  	if (buffer_new(&bh))
  		*new = 1;
  	else
  		*new = 0;
  	return ret;

  }
  
  /**

   * do_strip - Look for a layer a particular layer of the file and strip it off
   * @ip: the inode
   * @dibh: the dinode buffer
   * @bh: A buffer of pointers
   * @top: The first pointer in the buffer
   * @bottom: One more than the last pointer
   * @height: the height this buffer is at
   * @data: a pointer to a struct strip_mine
   *
   * Returns: errno
   */
  
  static int do_strip(struct gfs2_inode *ip, struct buffer_head *dibh,

  		    struct buffer_head *bh, __be64 *top, __be64 *bottom,

  		    unsigned int height, struct strip_mine *sm)

  {

  	struct gfs2_sbd *sdp = GFS2_SB(&ip->i_inode);

  	struct gfs2_rgrp_list rlist;

  	u64 bn, bstart;

  	u32 blen, btotal;

  	__be64 *p;

  	unsigned int rg_blocks = 0;
  	int metadata;
  	unsigned int revokes = 0;
  	int x;

  	int error = 0;

  
  	if (!*top)
  		sm->sm_first = 0;
  
  	if (height != sm->sm_height)
  		return 0;
  
  	if (sm->sm_first) {
  		top++;
  		sm->sm_first = 0;
  	}

  	metadata = (height != ip->i_height - 1);

  	if (metadata)
  		revokes = (height) ? sdp->sd_inptrs : sdp->sd_diptrs;

  	else if (ip->i_depth)
  		revokes = sdp->sd_inptrs;

  	memset(&rlist, 0, sizeof(struct gfs2_rgrp_list));
  	bstart = 0;
  	blen = 0;
  
  	for (p = top; p < bottom; p++) {
  		if (!*p)
  			continue;
  
  		bn = be64_to_cpu(*p);
  
  		if (bstart + blen == bn)
  			blen++;
  		else {
  			if (bstart)

  				gfs2_rlist_add(ip, &rlist, bstart);

  
  			bstart = bn;
  			blen = 1;
  		}
  	}
  
  	if (bstart)

  		gfs2_rlist_add(ip, &rlist, bstart);

  	else
  		goto out; /* Nothing to do */

  	gfs2_rlist_alloc(&rlist, LM_ST_EXCLUSIVE);

  
  	for (x = 0; x < rlist.rl_rgrps; x++) {
  		struct gfs2_rgrpd *rgd;

  		rgd = rlist.rl_ghs[x].gh_gl->gl_object;

  		rg_blocks += rgd->rd_length;

  	}
  
  	error = gfs2_glock_nq_m(rlist.rl_rgrps, rlist.rl_ghs);
  	if (error)
  		goto out_rlist;
  
  	error = gfs2_trans_begin(sdp, rg_blocks + RES_DINODE +
  				 RES_INDIRECT + RES_STATFS + RES_QUOTA,
  				 revokes);
  	if (error)
  		goto out_rg_gunlock;
  
  	down_write(&ip->i_rw_mutex);

  	gfs2_trans_add_bh(ip->i_gl, dibh, 1);
  	gfs2_trans_add_bh(ip->i_gl, bh, 1);

  
  	bstart = 0;
  	blen = 0;

  	btotal = 0;

  
  	for (p = top; p < bottom; p++) {
  		if (!*p)
  			continue;
  
  		bn = be64_to_cpu(*p);
  
  		if (bstart + blen == bn)
  			blen++;
  		else {
  			if (bstart) {

  				__gfs2_free_blocks(ip, bstart, blen, metadata);

  				btotal += blen;

  			}
  
  			bstart = bn;
  			blen = 1;
  		}
  
  		*p = 0;

  		gfs2_add_inode_blocks(&ip->i_inode, -1);

  	}
  	if (bstart) {

  		__gfs2_free_blocks(ip, bstart, blen, metadata);

  		btotal += blen;

  	}

  	gfs2_statfs_change(sdp, 0, +btotal, 0);
  	gfs2_quota_change(ip, -(s64)btotal, ip->i_inode.i_uid,
  			  ip->i_inode.i_gid);

  	ip->i_inode.i_mtime = ip->i_inode.i_ctime = CURRENT_TIME;

  	gfs2_dinode_out(ip, dibh->b_data);

  
  	up_write(&ip->i_rw_mutex);
  
  	gfs2_trans_end(sdp);

  out_rg_gunlock:

  	gfs2_glock_dq_m(rlist.rl_rgrps, rlist.rl_ghs);

  out_rlist:

  	gfs2_rlist_free(&rlist);

  out:

  	return error;
  }
  
  /**

   * recursive_scan - recursively scan through the end of a file
   * @ip: the inode
   * @dibh: the dinode buffer
   * @mp: the path through the metadata to the point to start
   * @height: the height the recursion is at
   * @block: the indirect block to look at
   * @first: 1 if this is the first block
   * @sm: data opaque to this function to pass to @bc
   *
   * When this is first called @height and @block should be zero and
   * @first should be 1.
   *
   * Returns: errno
   */
  
  static int recursive_scan(struct gfs2_inode *ip, struct buffer_head *dibh,
  			  struct metapath *mp, unsigned int height,
  			  u64 block, int first, struct strip_mine *sm)
  {
  	struct gfs2_sbd *sdp = GFS2_SB(&ip->i_inode);
  	struct buffer_head *bh = NULL;

  	__be64 *top, *bottom;

  	u64 bn;
  	int error;
  	int mh_size = sizeof(struct gfs2_meta_header);
  
  	if (!height) {
  		error = gfs2_meta_inode_buffer(ip, &bh);
  		if (error)
  			return error;
  		dibh = bh;
  
  		top = (__be64 *)(bh->b_data + sizeof(struct gfs2_dinode)) + mp->mp_list[0];
  		bottom = (__be64 *)(bh->b_data + sizeof(struct gfs2_dinode)) + sdp->sd_diptrs;
  	} else {
  		error = gfs2_meta_indirect_buffer(ip, height, block, 0, &bh);
  		if (error)
  			return error;
  
  		top = (__be64 *)(bh->b_data + mh_size) +
  				  (first ? mp->mp_list[height] : 0);
  
  		bottom = (__be64 *)(bh->b_data + mh_size) + sdp->sd_inptrs;
  	}
  
  	error = do_strip(ip, dibh, bh, top, bottom, height, sm);
  	if (error)
  		goto out;

  	if (height < ip->i_height - 1) {

  		gfs2_metapath_ra(ip->i_gl, bh, top);

  		for (; top < bottom; top++, first = 0) {
  			if (!*top)
  				continue;
  
  			bn = be64_to_cpu(*top);
  
  			error = recursive_scan(ip, dibh, mp, height + 1, bn,
  					       first, sm);
  			if (error)
  				break;
  		}

  	}

  out:
  	brelse(bh);
  	return error;
  }
  
  
  /**

   * gfs2_block_truncate_page - Deal with zeroing out data for truncate
   *
   * This is partly borrowed from ext3.
   */

  static int gfs2_block_truncate_page(struct address_space *mapping, loff_t from)

  {
  	struct inode *inode = mapping->host;
  	struct gfs2_inode *ip = GFS2_I(inode);

  	unsigned long index = from >> PAGE_CACHE_SHIFT;
  	unsigned offset = from & (PAGE_CACHE_SIZE-1);
  	unsigned blocksize, iblock, length, pos;
  	struct buffer_head *bh;
  	struct page *page;

  	int err;
  
  	page = grab_cache_page(mapping, index);
  	if (!page)
  		return 0;
  
  	blocksize = inode->i_sb->s_blocksize;
  	length = blocksize - (offset & (blocksize - 1));
  	iblock = index << (PAGE_CACHE_SHIFT - inode->i_sb->s_blocksize_bits);
  
  	if (!page_has_buffers(page))
  		create_empty_buffers(page, blocksize, 0);
  
  	/* Find the buffer that contains "offset" */
  	bh = page_buffers(page);
  	pos = blocksize;
  	while (offset >= pos) {
  		bh = bh->b_this_page;
  		iblock++;
  		pos += blocksize;
  	}
  
  	err = 0;
  
  	if (!buffer_mapped(bh)) {

  		gfs2_block_map(inode, iblock, bh, 0);

  		/* unmapped? It's a hole - nothing to do */
  		if (!buffer_mapped(bh))
  			goto unlock;
  	}
  
  	/* Ok, it's mapped. Make sure it's up-to-date */
  	if (PageUptodate(page))
  		set_buffer_uptodate(bh);
  
  	if (!buffer_uptodate(bh)) {
  		err = -EIO;
  		ll_rw_block(READ, 1, &bh);
  		wait_on_buffer(bh);
  		/* Uhhuh. Read error. Complain and punt. */
  		if (!buffer_uptodate(bh))
  			goto unlock;

  		err = 0;

  	}

  	if (!gfs2_is_writeback(ip))

  		gfs2_trans_add_bh(ip->i_gl, bh, 0);

  	zero_user(page, offset, length);

  	mark_buffer_dirty(bh);

  unlock:
  	unlock_page(page);
  	page_cache_release(page);
  	return err;
  }

  static int trunc_start(struct inode *inode, u64 oldsize, u64 newsize)

  {

  	struct gfs2_inode *ip = GFS2_I(inode);
  	struct gfs2_sbd *sdp = GFS2_SB(inode);
  	struct address_space *mapping = inode->i_mapping;

  	struct buffer_head *dibh;
  	int journaled = gfs2_is_jdata(ip);
  	int error;
  
  	error = gfs2_trans_begin(sdp,

  				 RES_DINODE + (journaled ? RES_JDATA : 0), 0);

  	if (error)
  		return error;
  
  	error = gfs2_meta_inode_buffer(ip, &dibh);
  	if (error)
  		goto out;

  	gfs2_trans_add_bh(ip->i_gl, dibh, 1);

  	if (gfs2_is_stuffed(ip)) {

  		gfs2_buffer_clear_tail(dibh, sizeof(struct gfs2_dinode) + newsize);

  	} else {

  		if (newsize & (u64)(sdp->sd_sb.sb_bsize - 1)) {
  			error = gfs2_block_truncate_page(mapping, newsize);
  			if (error)
  				goto out_brelse;

  		}

  		ip->i_diskflags |= GFS2_DIF_TRUNC_IN_PROG;

  	}

  	i_size_write(inode, newsize);

  	ip->i_inode.i_mtime = ip->i_inode.i_ctime = CURRENT_TIME;
  	gfs2_dinode_out(ip, dibh->b_data);

  	truncate_pagecache(inode, oldsize, newsize);
  out_brelse:
  	brelse(dibh);

  out:

  	gfs2_trans_end(sdp);

  	return error;
  }

  static int trunc_dealloc(struct gfs2_inode *ip, u64 size)

  {

  	struct gfs2_sbd *sdp = GFS2_SB(&ip->i_inode);

  	unsigned int height = ip->i_height;

  	u64 lblock;

  	struct metapath mp;
  	int error;
  
  	if (!size)
  		lblock = 0;

  	else

  		lblock = (size - 1) >> sdp->sd_sb.sb_bsize_shift;

  	find_metapath(sdp, lblock, &mp, ip->i_height);

  	if (!gfs2_qadata_get(ip))

  		return -ENOMEM;

  
  	error = gfs2_quota_hold(ip, NO_QUOTA_CHANGE, NO_QUOTA_CHANGE);
  	if (error)
  		goto out;
  
  	while (height--) {
  		struct strip_mine sm;
  		sm.sm_first = !!size;
  		sm.sm_height = height;

  		error = recursive_scan(ip, NULL, &mp, 0, 0, 1, &sm);

  		if (error)
  			break;
  	}
  
  	gfs2_quota_unhold(ip);

  out:

  	gfs2_qadata_put(ip);

  	return error;
  }
  
  static int trunc_end(struct gfs2_inode *ip)
  {

  	struct gfs2_sbd *sdp = GFS2_SB(&ip->i_inode);

  	struct buffer_head *dibh;
  	int error;
  
  	error = gfs2_trans_begin(sdp, RES_DINODE, 0);
  	if (error)
  		return error;
  
  	down_write(&ip->i_rw_mutex);
  
  	error = gfs2_meta_inode_buffer(ip, &dibh);
  	if (error)
  		goto out;

  	if (!i_size_read(&ip->i_inode)) {

  		ip->i_height = 0;

  		ip->i_goal = ip->i_no_addr;

  		gfs2_buffer_clear_tail(dibh, sizeof(struct gfs2_dinode));
  	}

  	ip->i_inode.i_mtime = ip->i_inode.i_ctime = CURRENT_TIME;

  	ip->i_diskflags &= ~GFS2_DIF_TRUNC_IN_PROG;

  	gfs2_trans_add_bh(ip->i_gl, dibh, 1);

  	gfs2_dinode_out(ip, dibh->b_data);

  	brelse(dibh);

  out:

  	up_write(&ip->i_rw_mutex);

  	gfs2_trans_end(sdp);

  	return error;
  }
  
  /**
   * do_shrink - make a file smaller

   * @inode: the inode
   * @oldsize: the current inode size
   * @newsize: the size to make the file

   *

   * Called with an exclusive lock on @inode. The @size must
   * be equal to or smaller than the current inode size.

   *
   * Returns: errno
   */

  static int do_shrink(struct inode *inode, u64 oldsize, u64 newsize)

  {

  	struct gfs2_inode *ip = GFS2_I(inode);

  	int error;

  	error = trunc_start(inode, oldsize, newsize);

  	if (error < 0)
  		return error;

  	if (gfs2_is_stuffed(ip))

  		return 0;

  	error = trunc_dealloc(ip, newsize);
  	if (error == 0)

  		error = trunc_end(ip);
  
  	return error;
  }

  void gfs2_trim_blocks(struct inode *inode)

  {

  	u64 size = inode->i_size;
  	int ret;
  
  	ret = do_shrink(inode, size, size);
  	WARN_ON(ret != 0);
  }
  
  /**
   * do_grow - Touch and update inode size
   * @inode: The inode
   * @size: The new size
   *
   * This function updates the timestamps on the inode and
   * may also increase the size of the inode. This function
   * must not be called with @size any smaller than the current
   * inode size.
   *
   * Although it is not strictly required to unstuff files here,
   * earlier versions of GFS2 have a bug in the stuffed file reading
   * code which will result in a buffer overrun if the size is larger
   * than the max stuffed file size. In order to prevent this from

   * occurring, such files are unstuffed, but in other cases we can

   * just update the inode size directly.
   *
   * Returns: 0 on success, or -ve on error
   */
  
  static int do_grow(struct inode *inode, u64 size)
  {
  	struct gfs2_inode *ip = GFS2_I(inode);
  	struct gfs2_sbd *sdp = GFS2_SB(inode);

  	struct buffer_head *dibh;

  	struct gfs2_qadata *qa = NULL;

  	int error;

  	if (gfs2_is_stuffed(ip) &&
  	    (size > (sdp->sd_sb.sb_bsize - sizeof(struct gfs2_dinode)))) {

  		qa = gfs2_qadata_get(ip);
  		if (qa == NULL)

  			return -ENOMEM;
  
  		error = gfs2_quota_lock_check(ip);
  		if (error)
  			goto do_grow_alloc_put;

  		error = gfs2_inplace_reserve(ip, 1);

  		if (error)
  			goto do_grow_qunlock;
  	}

  	error = gfs2_trans_begin(sdp, RES_DINODE + RES_STATFS + RES_RG_BIT, 0);

  	if (error)

  		goto do_grow_release;

  	if (qa) {

  		error = gfs2_unstuff_dinode(ip, NULL);
  		if (error)
  			goto do_end_trans;
  	}

  
  	error = gfs2_meta_inode_buffer(ip, &dibh);
  	if (error)

  		goto do_end_trans;

  	i_size_write(inode, size);

  	ip->i_inode.i_mtime = ip->i_inode.i_ctime = CURRENT_TIME;
  	gfs2_trans_add_bh(ip->i_gl, dibh, 1);
  	gfs2_dinode_out(ip, dibh->b_data);
  	brelse(dibh);

  do_end_trans:

  	gfs2_trans_end(sdp);

  do_grow_release:

  	if (qa) {

  		gfs2_inplace_release(ip);
  do_grow_qunlock:
  		gfs2_quota_unlock(ip);
  do_grow_alloc_put:

  		gfs2_qadata_put(ip);

  	}

  	return error;
  }

  /**

   * gfs2_setattr_size - make a file a given size
   * @inode: the inode
   * @newsize: the size to make the file

   *

   * The file size can grow, shrink, or stay the same size. This
   * is called holding i_mutex and an exclusive glock on the inode
   * in question.

   *
   * Returns: errno
   */

  int gfs2_setattr_size(struct inode *inode, u64 newsize)

  {

  	int ret;
  	u64 oldsize;

  	BUG_ON(!S_ISREG(inode->i_mode));

  	ret = inode_newsize_ok(inode, newsize);
  	if (ret)
  		return ret;

  	inode_dio_wait(inode);

  	oldsize = inode->i_size;
  	if (newsize >= oldsize)
  		return do_grow(inode, newsize);
  
  	return do_shrink(inode, oldsize, newsize);

  }
  
  int gfs2_truncatei_resume(struct gfs2_inode *ip)
  {
  	int error;

  	error = trunc_dealloc(ip, i_size_read(&ip->i_inode));

  	if (!error)
  		error = trunc_end(ip);
  	return error;
  }
  
  int gfs2_file_dealloc(struct gfs2_inode *ip)
  {
  	return trunc_dealloc(ip, 0);
  }
  
  /**

   * gfs2_write_alloc_required - figure out if a write will require an allocation
   * @ip: the file being written to
   * @offset: the offset to write to
   * @len: the number of bytes being written

   *

   * Returns: 1 if an alloc is required, 0 otherwise

   */

  int gfs2_write_alloc_required(struct gfs2_inode *ip, u64 offset,

  			      unsigned int len)

  {

  	struct gfs2_sbd *sdp = GFS2_SB(&ip->i_inode);

  	struct buffer_head bh;
  	unsigned int shift;
  	u64 lblock, lblock_stop, size;

  	u64 end_of_file;

  	if (!len)
  		return 0;
  
  	if (gfs2_is_stuffed(ip)) {
  		if (offset + len >
  		    sdp->sd_sb.sb_bsize - sizeof(struct gfs2_dinode))

  			return 1;

  		return 0;
  	}

  	shift = sdp->sd_sb.sb_bsize_shift;

  	BUG_ON(gfs2_is_dir(ip));

  	end_of_file = (i_size_read(&ip->i_inode) + sdp->sd_sb.sb_bsize - 1) >> shift;

  	lblock = offset >> shift;
  	lblock_stop = (offset + len + sdp->sd_sb.sb_bsize - 1) >> shift;
  	if (lblock_stop > end_of_file)

  		return 1;

  	size = (lblock_stop - lblock) << shift;
  	do {
  		bh.b_state = 0;
  		bh.b_size = size;
  		gfs2_block_map(&ip->i_inode, lblock, &bh, 0);
  		if (!buffer_mapped(&bh))

  			return 1;

  		size -= bh.b_size;
  		lblock += (bh.b_size >> ip->i_inode.i_blkbits);
  	} while(size > 0);

  
  	return 0;
  }